Inclusion Criteria

DISEASE CHARACTERISTICS:

- One of the following:

- Histologically confirmed high-grade glioma

- Glioblastoma multiforme

- Gliosarcoma

- Anaplastic astrocytoma

- Anaplastic oligodendroglioma

- Anaplastic mixed oligoastrocytoma

- Malignant glioma/astrocytoma, not otherwise specified

- Meningioma

- Hemangioblastoma

- Ependymoma

- Primitive neuroectodermal tumors

- Hemangiopericytoma

- Progressive glioma

- Clinically and radiographically diagnosed brain stem glioma

- Progressive or recurrent disease as determined by CT scan or MRI

- Biopsy allowed for prior recent (i.e., within the past 12 weeks) resection of
recurrent or progressive tumor

- Must have failed prior radiotherapy

PATIENT CHARACTERISTICS:

Age:

- 18 and over

Performance status:

- Karnofsky 60-100%

Life expectancy:

- More than 8 weeks

Hematopoietic:

- WBC at least 2,300/mm^3

- Platelet count at least 90,000/mm^3

- Hemoglobin at least 8 g/dL (transfusions allowed)

Hepatic:

- Bilirubin less than 3 times upper limit of normal (ULN)

- SGOT less than 3 times ULN

- No significant active hepatic disease

Renal:

- Creatinine less than 2.0 mg/dL OR

- Creatinine clearance at least 60 mL/min

- No significant active renal disease

Cardiovascular:

- No significant active cardiac disease

Other:

- No other malignancy within the past 3 years except nonmelanoma skin cancer or
carcinoma in situ of the cervix

- No significant active psychiatric disease

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception during and for 2 months after study

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- At least 2 weeks since prior interferon

- No concurrent immunotherapy

Chemotherapy:

- At least 6 weeks since prior nitrosoureas

- At least 4 weeks since prior temozolomide or carboplatin

- At least 3 weeks since prior procarbazine

- At least 2 weeks since prior vincristine

- At least 4 weeks since other prior cytotoxic chemotherapy

- No concurrent chemotherapy

Endocrine therapy:

- At least 2 weeks since prior tamoxifen

- Concurrent steroids allowed for control of the signs and symptoms of increased
intracranial pressure if on a stable dose for at least the past 5 days

Radiotherapy:

- See Disease Characteristics

- At least 2 weeks since prior radiotherapy

- No concurrent radiotherapy

Surgery:

- See Disease Characteristics

- At least 2 weeks since prior tumor resection

Other:

- At least 2 weeks since other prior noncytotoxic agents

- Concurrent enzyme-inducing antiepileptic drugs allowed

- No concurrent rifampin

- No concurrent grapefruit juice

- No other concurrent investigational agents